On Nov. 8, the ground simply vanished in Fukuoka, Japan. It was the work of a massive sinkhole.

The sinkhole began as two smaller holes before the middle portion of the multi-lane street collapsed, as you can see in the video above. The nearly 100-foot sinkhole resulted in power and gas utilities being shut down for much of the morning, but many had power restored by mid-afternoon. Gas remained shut down as crews checked for possible leaks.

The cause is under investigation, but work to expand subway tunnels in the city may be a possible culprit.

Speaking to the Japan Times, Nihon University professor Satoru Shimobe suggests multiple causes could be responsible. Shimobe, who specializes in geoenvironmental engineering and geotechnical engineering, says the Japanese sewage system as another possible reason the street collapsed. The pipes were constructed during country's expansion boom of the 1970s. Heavy rainfall in the area likely played a role as well.

Shimobe calls the increase of sinkholes "a growing social issue," with 4,000 to 5,000 occurring every year.

What a speedy recovery

Workers began working to fill the sinkhole almost immediately. The city government reached out to a soil company for assistance, and the sinkhole was filled with a mixture used to seal up cave-ins at old mines, according to the Japan Times. The sinkhole was filled in by the evening of Nov. 9, and the ground is said to be 30 times stronger than it was previously.

Officials kept the street closed until Nov. 15 to ensure maximum safety, and the city will also conduct surveys of the street every few hours for at least the next month.

Fukuoka officials have requested that an independent panel from the Land, Infrastructure, Transport and Tourism Ministry look into the cause of the sinkhole, which is still unknown.

This story was originally published earlier this month and has been updated with more recent information.